The present invention relates to ultraviolet lamps and, in particular, to metal halide lamps for producing high-intensity ultraviolet radiation.
It is known to use a metal halide lamp for producing ultraviolet radiation. U.S. Pat. No. 4,155,025 to Dobrusskin et al. discloses a high-pressure mercury-vapor discharge lamp having a filler including a halide together with a combination of at least two metals selected from iron, nickel and cobalt.
Japanese Patent No. 4929.869 discloses a lamp with a filler containing a halide together with mercury, iron and silver.
A-type ultraviolet radiation is typically defined as the region of the electromagnetic radiation spectrum with wavelengths between 315 and 400 nm. Wavelengths of major technological importance are generally in the range from 340 to 400 nm, and especially from 350 to 370 nm. However, the radiant efficiency of conventional lamps in these ranges is unacceptably low. Typically, 13-16% of the lamp's power is emitted as radiation of wavelengths between 340 and 400 nm, and 6-7% between 350 and 370 nm.
There is therefore a need for high-intensity ultraviolet lamps with improved radiant efficiency in the range of wavelengths from 340 to 400 nm, and especially from 350 to 370 nm.